The invention relates to an illumination device comprising:
(i) an electric lamp provided with: PA1 (ii) an associated reflector provided with: PA1 (iii) retention means for keeping the electric lamp with the electric element fixed to the reflector and aligned with respect thereto.
a light-transmitting lamp vessel which is closed in a gastight manner and which has an axis; PA2 an electric element arranged in the lamp vessel; PA2 a lamp cap provided with contacts and reference locations in a distributed arrangement around the axis, which lamp cap is fixed to the lamp vessel on the axis thereof, the electric element occupying a predetermined position with respect to the reference locations; PA2 current conductors connected to the electric element, issuing from the lamp vessel to the exterior, and connected to the contacts of the lamp cap; and PA2 a concave reflecting surface; PA2 an opening for introducing the lamp vessel into the reflector; PA2 alignment means in a distributed arrangement around the opening for cooperating with reference locations of the lamp cap so as to position the electric element in a predetermined location in the reflector; and furthermore comprising
Such an illumination device, a vehicle headlamp assembly, is known from U.S. Pat. No. 5,115,381.
In the known device, the lamp cap has circumference portions in the shape of circular arcs and lying adjacent one another, with respect to which the electric element of the lamp, an incandescent body, is positioned. Around the opening the reflector as two support surfaces lying on the legs of a V for the circular-arc-shaped circumference portions. When the lamp cap is brought into contact with the support surfaces by said circumference portions and is pressed home, the incandescent body will have a predetermined position relative to the reflector in two directions, x and y, transverse to the axis. The lamp cap and the reflector have additional means for achieving that the lamp and the reflector will be joined together in the correct mutual rotational positions. To obtain the desired position of the incandescent body in the reflector, however, the lamp is also to be brought into contact with the reflector in axial direction of the lamp vessel, the z-direction. The reflector has elevations around its opening and the lamp cap has elevations distributed around the axis for achieving an accurate definition of this abutment.
A discharge lamp for use in a reflector of a vehicle headlamp is known from U.S. Pat. No. 5,216,319, where a similarly shaped synthetic-resin lamp cap can be provided in a reflector in a similar manner, with its pair of electrodes in a previously defined position. The lamp cap has a circular circumference with a recess for determining its rotational position in the reflector. To define the depth to which the lamp can enter the reflector, i.e. the location of the electric element in the z-direction, the lamp cap has elevations distributed over a surface which is transverse to the axis, which elevations will abut against the reflector.
Lamps having similar lamp caps for similar uses in reflectors are also known from: U.S. Pat. No. 5,320,562, U.S. Pat. No. 5,461,277, U.S. Pat. No. 5,412,275, U.S. Pat. No. 5,378,958, U.S. Pat. No. 5,527,199, U.S. Pat. No. 5,619,102, U.S. Pat. No. 5,541,471, U.S. Pat. No. 5,479,066, EP-A-0 570 068, EP-A-0 774 158, EP-A-0 710 396, EP-A-0 708 978 and EP-A-0 767 968.
The lamp cap is fixed to the lamp vessel by mechanical means in the above known lamps. A clamping member is for this purpose present around the lamp vessel, retaining the lamp vessel and fixed to the lamp vessel after the electric element had been brought into a predetermined position in relation to the reference locations of the lamp cap. Alternatively, however, the lamp vessel may be connected in the correct alignment to a lamp cap by means of, for example, cement.
It is a disadvantage of the known device and of the known lamps suitable for this device that the lamp cap must be pressed home both in the (x, y) plane and perpendicular thereto, in the z-direction, and that the positioning of the lamp cap can be hampered thereby.